Britney Spears Calls Sister Jamie Lynn 'Bitch' in Rambling Car Video

Britney Spears is back to attacking her little sister, Jamie Lynn Spears -- out here calling her a "bitch" ... this while going on and on about things that just don't make sense.

The pop star posted a few since-deleted videos to her Instagram Story Tuesday, which features her in the passenger seat of a car ... with three other people with her, including what appears to be her assistant -- at least that's how Brit describes her anyway.

The footage is strange ... the group is going up the side of some mountain, following a Jeep that seems to be leading them somewhere remote. Britney and the gang say they're going horseback riding -- which, if accurate, jibes with other posts of hers from earlier in the week.

Everything seems relatively innocent at first, but right off the bat ... it's clear BS is using this as a way to take a shot at JLS -- as well as her stint on 'I'm a Celebrity ... Get Me Out of Here!'

Take a listen ... Britney says they're heading into the "jungle" ... where she says Jamie was getting "bathed" on TV. She's referring to Jamie Lynn's time on the show ... and took the opportunity to call Jamie Lynn a "little s***" and a "little bitch" repeatedly in the diatribe.

Britney's also going in and out of accents here -- apparently trying to match her female cohort's British accent. She talks about getting a vagina rash by peeing in the bushes.

Britney then goes on to joke about running out of wine, and then calling her manager to fly her and her friends somewhere on a helicopter ... but only with BS's favorite pilot, who she has a crush on. Yeah ... like we said, it's all over the place -- and isn't very coherent at all.

What's interesting of course is that Brit is carrying on with her life like nothing's amiss -- even though we've been assured things are falling apart at the seams for her, and it's dire.

We know she's blowing through cash at a rapid pace ... and that she's in danger of running the well dry. While she's clearly kidding in this clip, her chopper reference is ... well, telling.